Two weeks ago, Jose Pimentel was arrested as an alleged terrorist bomb-maker as a result of an NYPD sting. Within hours of the arrest, his attorney raised the prospect of a possible entrapment defense. Last month, when Mansour Arbabsiar was indicted for trying to assassinate the Saudi ambassador to the United States on behalf of Iran, he, too, was the subject of a sting, in this case by the FBI, and he claimed entrapment. These are but the latest iterations of dozens of terrorism cases that have come through the system with varying degrees of "entrapment" claims by the defense at the time of arrest. The Fort Dix case from New Jersey in 2007, and the more recent instances of the sole terrorism suspects in Portland, Washington, DC and Baltimore are among the many cases in which some sort of entrapment was alleged (at least, at the outset).

This is a problem in a counterterrorism world where law enforcement relies on preventive stings as its main strategy. By definition, the strategy precludes a defense. Legally, entrapment is mostly about the suspect's predisposition because the other element of entrapment, inducement by the government to commit the crime, is usually not disputed. Thus, if the government can show that the defendant was inclined to the crime, then the entrapment-by-inducement defense cannot prevail in court. In a terrorism case, the fact of being willing to commit an act of terrorism is seen as predisposition, no matter how much of a Catch-22 this may be. As a result, lawyers rarely choose to mount the defense.

This explains why, when terrorism cases come to trial, entrapment is rarely part of the legal strategy of the defense. Since 2001, ten defendants have claimed entrapment; none has succeeded in winning an acquittal. Even more telling is the discontinuity between the initial claims of entrapment and the mounting of an entrapment defense at court. In short, if a suspicion of entrapment seems a viable starting-point for a defense, forget it. Find another strategy with which to defend your client.

Perhaps because of this perfect scenario in which the strategy employed denies a defense, there has been very little thought given to making law enforcement accountable for overreaching. The strategy is so temptingly successful: as long as the defense has no workable legal redress, why limit the aggressiveness of the government's strategy?

And, in fact, this is what has happened. In case after case, the government has gone from being an agency that waits and watches for criminal activity that is terrorist, to becoming an agency that appears comfortable designing and helping implement the crime. The most egregious example thus far was the recent Riverdale Synagogue Case, in which the informant, a Pakistani-American, provided not only the ideas for the target and the weapons, but also took the lead in terms of teaching the main defendant about the ways in which "cause" of jihad might grow out of the defendant's own strongly antisemitic views. As the judge admitted at sentencing:

"The essence of what occurred here was that a government, understandably zealous to protect its citizens, created acts of terrorism out of the fantasies and the bravado and the bigotry of one man in particular and four men generally, and then made these fantasies come true."

So, too, the government has not been held to account for the size of the incentives it offers in exchange for agreeing to commit acts of jihad. In the Bronx case, the main defendant, James Cromitie, refused government offers until he lost his income and was offered a staggering $250,000. His co-defendant, David Williams, was offered a liver transplant for his dying brother. Yet another defendant – poor, mentally challenged and hungry – was given food when he came to planning meetings, which tapes show he barely participated in, beyond eating.

Admittedly, the Riverdale case appears to be in a class of its own in terms of government overreach, but these are not the only cases of government preying upon vulnerable individuals. There have certainly been terrorism sting operations in which informants were used in accordance with the spirit of the law – cases in which the FBI was intercepting a crime already in progress, rather than creating it out of whole cloth. The recent Arbabsiar case may turn out to be such an example; the government claims that it became involved in the case after the defendant initiated discussions with the informant about assassinating the Saudi ambassador, and that the defendant himself arranged many details of the planned conspiracy.

Nevertheless, there are too many cases where the government's involvement in the case traverses into a gray zone of leading, rather than following, the crime. In 2006, an informant enticed a reluctant pizza shop owner who became desperate for funds to save his business to launder funds for the purchase of a missile aimed at American citizens. More recently, the government has seemingly influenced several very young Muslim men – including Antonio Martinez in Baltimore and Mohamed Osman Mohamud in Portland – to turn anger and talk about violence into a willingness to conduct actual acts of violence involving weapons.

There is a world of difference between stings that begin with the defendant's initial attempts, however minor, to commit a violent crime and ones that seek to see if law enforcement can entice someone to commit a violent crime in the name of jihad – and provide the means and method to do so. More importantly, there is a world of difference between law enforcement that makes us safe from those with the intent and know-how to harm us and those who are groomed to commit a crime – and sometimes even coached in the ideology – by law enforcement agencies.

Aside from questions of justice, this is not a risk-free strategy: once federal agents teach someone how to commit to jihad, build a bomb or surveil a target, they cannot fully control whom that individual may relay these lessons prior to his arrest – or even afterward in a prison environment. The problem with entrapment is not just that it may be unfair to defendants. The danger is that it compromises the public's understanding of the actual threat; in so doing, it may ultimately compromise public security itself.